1. Field of the Invention
The present invention relates to an expansion dowel that includes a cylindrical body having an expandable region, a plurality of axial slots extendable to a front, in the setting direction, end of the body, and a through--bore tapering in the setting direction in the region of the axial slots, with the dowel further including an expansion member located in the through-bore, axially displaceable relative to the cylindrical body, and fixable in the bore in its end position.
2. Description of the Prior Art
In the attachment technology, an expansion dowel, which includes a dowel body provided with a slot and having a conical bore tapering in a setting direction, and a conical expansion member axially displaceable in the bore of the dowel body, is often used. The displacement of the expansion member is effected by applying axial blows with a hammer or the like to the expansion member via a pin-shaped setting tool. During a preliminary driving-in of the expansion member, the dowel body is radially expanded and becomes thereby anchored in a bore of a structural component. With these impact-driven expansion dowels, which a usually formed of metal, attachments are effected quickly and in a simple manner. A drawback of the known expansion dowel consists in that it does not have a second expansion function in an expandable bore. Therefore, its range of applications, as a rule, is limited merely to the pressure zone of a structural component.
In order to achieve a certain secondary expansion characteristic with such an expansion dowel, solutions were proposed which contemplated fixing of the expansion member in the bore of a structural component during driving of the expansion member through the bore formed in the dowel body. Such a dowel is disclosed, e.g., in German patent publication DE-A-33 09 006. The disclosed expansion dowel has a cylindrical dowel body having axial slots formed at the front e nd of the body and opening in a setting direction and a through-bore. An expansion member is displaced axially in the through-bore upon radial expansion of the dowel body. On the circumference of the expansion member, there are provided radially projecting wedge cams which, on one hand, serve for radial expansion of the dowel body and, on another hand, should provide for fixing of the expansion member in the structural component to insure that the dowel body can further expand upon application of a load to the dowel body. The wedge cams are displaced into the expanded regions of the axial slots and project beyond the circumference of the dowel body. During driving of the dowel in and displacement of the expansion member, the wedge cams engage the wall of the bore formed in the structural component and form grooves in the bore wall which extend a longitudinal direction. The grooves extend from the bore mouth and have a depth corresponding to the radially projecting length of the wedge cams from the circumference of the dowel body. With an opening fissure, there is a danger of the expansion member drifting, during application of a load to the dowel, along the grooves toward the bore mouth and being pulled out of the bore.
Accordingly, an object of the present invention is to eliminate the drawbacks of the prior art expansion dowel. Another object of the present invention is to provide an expansion dowel which is suitable for use in a zone, which is subjected to tensile stresses, and which has adequate secondary expansion characteristics in order to prevent a sudden failure of an attachment point. At that, the expenses associated with anchoring of an inventive expansion dowel should remain the same as expenses associated with anchoring of a prior art dowel, and no additional operational steps should be necessary.